firewall centos

when the httpd server not accesible from outside then you just

Firewall

Notice that in some versions of CentOS, a firewall is installed by default which will block access to port 80, on which Apache runs. The following command will open this port:

sudo iptables -I INPUT -p tcp --dport 80 -j ACCEPT

Remember to save your firewall rules after adding that instruction so your web server will be accessible the next time you reboot:

sudo service iptables save

setting java home linux centos 6.6

alternatives config java

 

  Selection    Command
   1           /usr/java/jdk1.6.0_26/jre/bin/java
   2           /usr/lib/jvm/jre1.6.0openjdk/bin/java
   3           /usr/java/jdk1.7.0_55/jre/bin/java
*+ 4           /usr/java/jdk1.8.0_25/jre/bin/java
press 3
copy path from list above